Surface arc antechamber spark plug



31, 1954 G. F. WRIGHT ETAL 2,687,713

SURFACE ARC ANTECHAMBER SPARK PLUG Filed Aug. 14, 1951 IN V EN TOR. G/ZBEET F We/Gf/ 7- Wwzm ' plu shown inFigure Patented Aug. 31, 1954 2,687,713 SURFACE ARC ANTECHAMBER, SPARK PLUG,

Gilbert F. Wright, Benton, and Gaylord W. Newassignors to Boeing Air- 1 ton, Seattle, Wash., wplane Company, Sea

of Delaware ttle, Wash., a corporation Application August 14, 1951, Serial No. 241,811

at the end of the antechamber remote from its opening.

In surface are spark plugs the arc is not struck between two point electrodes, but diffuses between two electrodes of substantial area across an intervening surface. In such a spark plug it is an object .tomaintain the surface across which the arc diffusesfree from deposits of carbon and lead compounds. 1 i a A more specific object is to accelerate the propagation of combustion in the antechamberof an antechamber spark plug mechanism so as to increase the intensity ofthe flame projected from the antechamber into the principal combustion space and to reduce the'duration of such flame projection so as to expedite the ignition of the entire charge of combustible mixture in the principal combustion space, such as an engine cylinder.

In the design of such a surface are antechamber spark plug it is a further object to utilize simple construction which will expedite manufacture of the sparkplug.

Additional features and advantages of the structures shown as examples in the accompanyingndrawings are discussed in the following specific description. Y

Figure 1 is a longitudinal sectional view through one type of spark plug mechanism ininvention, the core being shown in side elevation;

I FigureZ is a fragmentary longitudinal sectional view through a different type of spark plug mechanism. with the core shown in side elevation, and Figure 3. is a transverse sectional view of this spark. plug taken on line 3-3 of Figure 2.

Figure 4. is a fragmentary longitudinal section through another spark plug modification, a side view'of the core being shown, and Figure is a transverse sectional view through the spark 4 on line 5-5 of that figure. I Figure 6 is a fragmentary longitudinal sectional view through still a, different embodiment of the spark plug withrthe core in side elevation, and Figure 7 is a transverse sectional view of this spark plugon line 1-1 of Figure 6.

The spark plug shown in. Figure 1 includesthe metal body Linwhichthe insulating core2, preferably of ceramic materialisreceived." H'I'hfi inner 19 Claims. (01. 123-169) end of this body is of reduced size and has an external thread It] adapted to be screwed into the spark plugreceivingport of an internal combustion engine. Within thisreduced portion the antechamber cavity H which has a mouth 12 opening through the inner end of the spark plug. The shape and size of the antechamber I l is similar to that shown in Wright application Serial No. 163,155, now Patent No. 2,642,054, except that the core 2 is not spaced from the body lover any appreciable distance lengthwise of the spark plug.

In a surface are type'of spark plug the spark does not jump cleanly through an air gap be tween two electrodes. On the contrary, the area of both electrodes between which the spark travelsis rather large, and such electrode areas in each case are adjacent to opposite sides of an intervening surface along which the electricityv flows. In such a surface arctype of spark plug considerably lower voltage is required than in the jump spark type of spark plug, althoughthe current utilized is higher. The fouling problem by deposit of carbon or lead compoundsfrom gasoline is very materially reduced because there are no narrow spaces where such foreign substances can accumulate, and moreover, slight deposits of foreign material do-not interfere nearly as much with eflicient operation of the spark plug.

In the form of spark plu shown in Figure 1 the shoulder I 3 at the closed end of the antechamber l l is integral with the body I, and on its outer side has a sloping seat for the ceramic core 2. The inner end of the core has an end tapered complementally to such sea, which is pressed against a sealing ring 20 interposed between such core end and its seat. In this relationship the central electrode 2| 1 extending through the core 2 is disposed at the center of the circle formed by the inner peripher of the shoulder I3.

The shoulder 13 then serves as the grounded electrode for the spark plug so that when a voltage is impressed between the electrode 2| and the body I a sheet electrode 2| and the shoulder l3 across the space 22 of the inner end of core 2, This spark will ignite the combustible mixture in the antechame ber ll, projecting an intense tongue of flame through the aperture I 2 into th engines combustion chamber. 1 I

The core 2 is held in the position shown in Figure 1 by the securing ring 23 which is pressed against the copper gasket ring 24, preferably of circular cross section, bearing against the core flange 25. The securing ring 23 is held in place after the ceramic core has been seated firmly in arc will be struck between the the cylindrical portion of.

the outer edge M of the body core into over- 23 as shown in the body cavity by I being bent inwardly toward the lapping relationship to the ring Figure 1.

With the exception of the particular arrangement of electrodes and their structure, the cores 2 and bo diesili of the spark plugs shown in Figures 2, land 6 are the same as the corresponding elements in the spark plug of Figure 1. Consequently, it is not necessary to describe such structure of each of these spark plugs in detail, and the following description is confined principally to the electrode arrangement.

Whereas in the spark plug of Figure .1 the-concentric electrodes 2| and I3 were disposed substantially coplanar so that the intervening surface across which the arc is struck by a ring defining a plane disposed transversely of the axis of the spark plug, the central electrode of the spark plug in Figures 2 and 3 is a plate 26 disposed in a plane spaced longitudinally of the spark plug inwardly from the plane of the shoulder t3. Thesurface 21 across which the arc diffusesi-n a spark plug of this construction is of cylindrical shape, the axis of which is coaxial with the longitudinal axis of the spark plug and is formed by a cylindrical tip on the inner end of the core. The disk 2:6 is slightly larger than the cross section of this tip so that its peripheral portion :forms a circumferential rib or rim constituting one electrode which cooperates with the grounded electrode formed by the shoulder l3.

Disk-.26 is slightly smallerthan the mouth 12 of the antechamber, so that :after the core 2 has been assembled with the body I in the manner described the conductor 2! for the central electrode disk which it carries may be inserted through the mouth of the ante'charnber and threaded through,. the central bore in the core to locate and hold in place the electrode disk 26.

The electrode construction of the spark plug shown in Figures 4 and 5 is generally similar to that of Figure '2 except that in this instance the electrode disk 25 is considerably smaller than the core tip which projects through the aperture within the. shoulder 13.. Consequently, between the cylindrical portion of the core tip and the electrode disk 26' is a surface across which the arc is struck of truncated. conical 'iorm tapered from the core tip toward the inner end of the spark plug. The base of this truncated conical portion may lie in therplane of theshoulder 13 at the closed :end of the antechamber 11., or if it is desired to locate the surface :across which the arc is struck closer tothe mouth of the antech'a'mber, a cylindrical collar 13' can be provided. extending from the shoulder [3' to the base of the conical 'portionwof the core tip.

Because the disk 26' in this instance is smaller than the cylindrical: portion of the core tip and the aperture in shoulder 13 through which it projects, the central electrode can be assembled.

with the core '2' prior to the inner end of the core being inserted into the spark plug body I'. The same procedure would be followed in fabrication of the spark plug-shown in Figure l.

In Figures '6 and '7 as in Figure l the surface 22 across which the arc is struck is disposed in a; plane perpendicular to the longitudinal axis of the spark plug. Instead of such surf-ace being annular, however, it is'in the form of the base ofa groove 22" between-the grounded plate electrode l5 and the electrode -2 8connected to the conductor 2|. "In this construction as in the sti'tuting the portion of face complemental having a bottom 22 spark plug of Figure 2 the tip of the core 2 is cylindrical, but the grounded electrode I 5 may actually be carried by the core. Thus this electrode may be formed integral with an arcuate strip 16 embracing a minor arcuate portion of the core tip. Ihe outer end of this strip is integral with a, ring I! having an inclined outer to an outwardly flaring seat formed on the body shoulder I3.

"The grounded electrode [5 is thus in the shape of .a circular segment having its chordal edge spaced from the chord-a1 edge of the electrode .28 which also is planar and shaped as a circular segment. "The altitudes of the two segments should be substatially equal; their bases should be parallel and spaced apart to define a groove of the width desired across which the arc is to be struck. It will be evident that so long as the adjacent edges of the electrodes I5 and 28 are parallel and these electrodes are coplanar it is immaterial so far as the opera.- tion of the spark-plug :is concerned what their particular shape is, and consequently they may be rectangular, triangular or of other polygonal shape and need not even be of the same shape as long as the adjacent edges are of substantially equallengths. The segmental shapes of the electrodes l5 and 28 are, however, convenient for the type of assembly illustrated in which these electrodes :are assembled on the inner end of the core 2 before it is inserted into the body, and then the ring I] is pressed into its seat when the inner core end is inserted into the body,

In all the spark plugs discussed it is evident that the surface across which the arc is propagated is located in the antechamber -Il remote from its mount 12 and. in the spark plugs of .Figures 1 and 2 is located adjacent to the closed end of the antechamber. The are will therefore ignite initially the combustible mixture in "the ante chamber;v and as it expands during burning such combustible mixture will eject a, tongue of intense flame from the ant'echamber through its mouth l2 to propagate very rapidly ignition of all the combustible mixture in the engine combustion space into -which the antechamb'er I'I opens.

We claim as our invention:

.1. fipark plug mechanism comprising a metal body defining an antechamber of an axial extent approximately equal to its maximum width and having. a mouth opening through the inner end of :said' body of a width approximately half the maximum width of the antechambe'r an insulating core having its. inner end received in said body,..an electrode carried by said core, disposed in. said antechamber remote from the mouth thereof and spaced from said body, and an interv'ening insulating material surface at a location between said electrode and the adjacent portion of said *body where such electrode and body are at least its close together 'as at any other location for diffusion of an arc thereacross be tweensa'id. electrode and-said body portion.

2;. spark plug mechanism 'defined in claim 1', and a plate substantially perpendicular to the axis of the sparkzplug and carried by the core adjoining such intervening insulating: material surface, constituting such core-carried electrode.

3'. The spark plug mechanism defined in claim 1,. end-a shoulder .on the body within the antechamber remote .from'its mouth, adjoining such intervening insulating material surface and 'conthe body adjacent to' the electrode between which shoulder and the electrode the arc is diffused.

4. Spark plug mechanism comprising a metal body defining an antechamber having a mouth opening through the inner end of said body of a Width approximately half the maximum width of the antechamber, an insulating core having its inner end received in said body, and an electrode carried by said core, disposed in said antechamber remote from the mouth thereof and spaced from said body, the inner end of said core adjoining a portion of said electrode and a portion of said body at least as close together as any other portions of said electrode and body and defining an intervening insulating material surface for diffusion of an arc thereacross between said electrode and said body.

5. Spark plug mechanism comprising a metal body defining an antechamber having a mouth opening through theinner end of said body of a width approximately half the maximum width of the antechamber, an insulating core having its inner end received in said body, an electrode carried by said core, disposed in said antechamber remote from the mouth thereof and spaced from said body, and an intervening insulating.

material surface disposed in a plane substantially perpendicular to the axis of the spark plug at a location between said electrode and a portion of said body where such electrode and body are at least as close together as at any other location for diffusion of an arc thereacross between said electrode and said body portion.

6. The spark plug mechanism defined in claim 5, and a shoulder on the body within the antechamber adjacent to the intervening insulating material surface and constituting the portion of the body between which portion and the electrode the arc is struck.

'7. Spark plug mechanism comprising a metal body defining an antechamber having a mouth opening through the inner end of said body, an insulating core having its inner end received in said body, an electrode carried by said core, disposed in said antechamber remote from the mouth thereof and spaced from said body, and an intervening insulating material surface of substantially cylindrical shape and disposed substantially coaxial with the spark plug axis between said electrode and a portion of said body for diffusion of an arc thereacross between such body portion and said electrode.

8. Spark plug mechanism comprising a metal body defining an antechamber having a mouth opening through the inner end of said body, an insulating core havingits inner end received in said body and including a tip portion of insulating material projecting into said antechamber, an electrode carried by said core, disposed in said antechamber remote from and spaced from said body and projecting beyond said insulating core tip, and a shoulder projecting from said body into said antechamber at a location farther from the mouth thereof than the end of said core tip for diffusion of an are between said electrode and said shoulder across the intervening surface of said core tip.

9. The spark plug mechanism defined in claim 8, and a plate carried by the core tip, in a plane substantially perpendicular to the axis of the spark plug, of a width greater than the width of such tip and constitutingthe electrode.

.plate for diffusion of an 10. The spark plug mechanism defined in claim 9, in which the core tip includes a portion of cylindrical shape.

11. The spark plug mechanism defined in claim 8, in which the core tip includes an end portion of frustoconical shape.

12. The spark plug mechanism defined in claim 11, and a plate carried by the core tip in a plane substantially perpendicular to the axis of the spark plug, of a width greater than the width of the tip end and constituting the electrode.

13. The spark plug mechanism defined in claim 12, and the shoulder including a collar extending generally axially of the spark plug, encircling the core tip and having its edge closer to the antechamber mouth spaced from the electrode arc across the frustoconical surface of the tip between said collar and the electrode plate.

14. The spark plug mechanism defined in claim 8, a plate carried by the core tip substantially in a plane perpendicular to the axis of the spark plug, constituting the electrode, and a plate substantially coplanar with said electrode plate, spaced edgewise therefrom and grounded to the spark plug body.

15. The spark plug mechanism defined in claim 14, in which the adjacent edges of the plates are parallel over a substantial distance.

16. The spark plug defined in claim 15, in which the parallel edges of the plates are straight and of substantially equal length.

17. The spark plug defined in claim 16, in which the plates are substantially of the same size and shape and are arranged symmetrically about the longitudinal axis of the spark plug.

18. The spark plug defined in claim 17, in which the plates are of circular segmental shape having their bases in spaced parallel relationship.

19. Spark plug mechanism comprising a metal body defining an antechamber having .a mouth opening through the inner end of said body of a width approximately half the maximum width of the antechamber, an insulating core having its inner end received in said body, an electrode plate carried by said core and disposed in said antechamber remote from the mouth thereof, a second plate disposed substantially coplanar with said electrode plate, spaced edgewise therefrom and grounded to said body, and an intervening insulating material surface between said two plates for diffusion of an arc thereacross between said plates.

References Cited in the file of this patent UNITED STATES PATENTS 

